Each session in MySQL has a session time zone (STZ). This is the
session time_zone value that is
initialized from the server's global
time_zone value when the session
begins but may be changed during the session.

The session time zone that is current when a
CREATE EVENT or
ALTER EVENT statement executes is
used to interpret times specified in the event definition. This
becomes the event time zone (ETZ); that is, the time zone that is
used for event scheduling and is in effect within the event as it
executes.

For representation of event information in the
mysql.event table, the
execute_at, starts, and
ends times are converted to UTC and stored
along with the event time zone. This enables event execution to
proceed as defined regardless of any subsequent changes to the
server time zone or daylight saving time effects. The
last_executed time is also stored in UTC.

If you select information from mysql.event, the
times just mentioned are retrieved as UTC values. These times can
also be obtained by selecting from the
INFORMATION_SCHEMA.EVENTS table or
from SHOW EVENTS, but they are
reported as ETZ values. Other times available from these sources
indicate when an event was created or last altered; these are
displayed as STZ values. The following table summarizes
representation of event times.

The preceding table applies for MySQL 5.1.17 and up. Prior to
MySQL 5.1.17, the event time zone is not stored in the
mysql.event table or available from
INFORMATION_SCHEMA.EVENTS or
SHOW EVENTS. Times that are
displayed using ETZ from 5.1.17 and up are displayed in UTC before
5.1.17, as shown in the following table.